4 cylinder motorbike engine won't stay running. Fuel is injected in. The sparks are all working. It will start running sometimes and only keep going with near full throttle which will hold engine at less than tick over until it eventually stops.

Smart Fortwo C1446 Possible Solution : The crankshaft sensor signals the fuel injection computer or the ignition control when the cylinders are firing. This causes the ignition coil to provide a spark and the injector to inject fuel into each cylinder at the right time.If either sensor isn't working correctly, the car will run rough and the engine will be less efficient. In later car models, the car's computer can usually keep the vehicle running, but the engine warning light on the dashboard goes on to warn the driver

why does the blue box say 2005 swift and 03 polo?, confusing , so I will answer in the generic. (any modern car)

any engine dies for vast reasons, I have a list of 50 .
but breaks down to 4. (in pure physics) Otto cycle engines, GAS.

1: lost DC 12volt power to the EFI system( electronic fuel injection)
2: lost compression on more or all cylinders, 150psi min. is a goal.
3: lost spark, weak spark or mal-timed spark.
4: bad fueling, (too little , or too rich fuel injection)

The ECU works hard to sustain running, via idle speed control valve
and spark timing tricks.
when the above 4 go bad, the ISC function fails and the engine
stalls.
so does, skipping 60,000 mile tuneups. that cause any of the 4.

Gas, air, compression, and spark is all the cylinders need for the engine to run. No start is usually gas or spark related. Here's the fuel check on fuel injected cars. Turning the key to on will start the pump for 2 or 3 seconds to pressurize the system. When the engine is cranking over the computer turns on the fuel pump relay again, so the pump will be on. And stays on after engine is running to keep high pressure against the fuel injectors. The computer times the injector pulse to spray gas into the intake or into the cylinder at the right time.
So if you have a no start, to check for gas, listen for the pump- a distinctive hum or buzz from the tank, check the fuel pump fuse, see if you can feel or hear the fuel pump relay click when someone turns the key to on. (Did you remember to check if the tank has gas?). Finally, you would have to check for power on the fuel pump wire at the tank connector, while someone holds the key in start. If you have power there, it's likely you need a new fuel pump. If the pump is working, well and good, but keep in the back of your mind that a weak pump that puts out low pressure can cause hard starting problems and poor running. At any rate, if you have gas up to the fuel rail, the only other thing between there and the cylinders is the injectors. Are they working? A quick check would be to remove a spark plug or two after cranking the engine over a few seconds. If they are wet with gas, the injectors are injecting. Hope I've helped you out some. I know some people who say to spray some starting fluid into the air intake to check if you have a gas problem with starting- I've done it myself. But I've learned it's better to use carburetor cleaner spray instead, it burns cleaner and something about the potentially harmful effects of starting fluid, well. good luck.

What engine ? 4.3 , 4.8 , 5.3 or 6.0 l What fuel injection system ? What is the fuel pressure ? Do you know what fuel trims are ? The fuel pressure regulator's are prone to leaking to leaking on thses SPI injection system./
How to identify and repair leaking fuel pressure regulator GM CPI system...

If your vehicle is fuel injected I would say you have a blown fuel regulator. This would cause excess fuel into the cylinders (flooding) causing a miss and coughing and also blow fuel into the air breather. If will also cause the vehicle to run poorly and could cause the vehicle to stall. Also to much fuel on startup can flood the cylinders and cause the vehicle to no start.

The engine is port fuel injected, so there are injectors for each cylinder.
Why did you replace one injector ??
Have you checked for spark at the plugs and fuel pressure ?

On electronic fuel injection pumping an pumping an pumping the gas pedal does nothing without the engine running ! Pushing the gas pedal to the floor will cause the PCM - engine computer to go into clear flood mode .

You have some very interesting ideas here , but not really how it works or is !

The vehicle will go into closed loop fuel control when the engine coolant temp reaches a definded temp an the O2 sensor get hot.

She would run for a couple minutes and die which is open loop when running, closed loop is when the sensors kick and it would die. Pulled spark plugs, they were black meaning no spark. Can only be 2

Black spark plugs indecate a rich condition , over fueled , wet spark plugs indecate no spark .

Fuel pressure at idle is normally 30-35psi. Start by taking the gas cap off, and putting it back on. That will De-pressurize the fuel system. Also, make sure you have gas in the car. I have seen gauges on these cars read wrong. I hope this helps.

You said, 'fuel injectors are not injecting fuel into fuel rail' but it's my understanding that the fuel rail gasoline is supplied by the pump, and the fuel injectors just pulse to allow fuel to get to the cylinders. I would check out the fuel delivery problem further. Check for pressure in the fuel rail that is within specs.

If not, then the pump or fuel pressure regulator may be the problem. Check the fuse for the fuel pump. If good, then the pump may be bad in the tank.

Good luck on this.

Is your cat. convertor blocking up? If it is this condition, it could very well be the problem. Disconnect the convertor start the car & see if it takes the gas well. If it does, change the cat. convertor. Good luck!